High-throughput HDP-CVD processes for advanced gapfill applications

ABSTRACT

Methods are provided of depositing a silicon oxide film on a substrate disposed in a substrate processing chamber. The substrate has a gap formed between adjacent raised surfaces. A silicon-containing gas, an oxygen-containing gas, and a fluent gas are flowed into the substrate processing chamber. The fluent gas has an average molecular weight less than 5 amu. A first high-density plasma is formed from the silicon-containing gas, the oxygen-containing gas, and the fluent gas to deposit a first portion of the silicon oxide film over the substrate and within the gap with a first deposition process that has simultaneous deposition and sputtering components having relative contributions defined by a first deposition/sputter ratio. A second high-density plasma is formed from the silicon-containing gas, the oxygen-containing gas, and the fluent gas to deposit a second portion of the silicon oxide film over the substrate and within the gap with a second deposition process that has simultaneous deposition and sputtering components having relative contributions defined by a second deposition/sputter ratio. The second deposition/sputter ratio is less than the first deposition/sputter ratio. Each of the first and second deposition/sputter ratios is defined as a ratio of a sum of a net deposition rate and a blanket sputtering rate to the blanket sputtering rate.

BACKGROUND OF THE INVENTION

One of the persistent challenges faced in the development ofsemiconductor technology is the desire to increase the density ofcircuit elements and interconnections on substrates without introducingspurious interactions between them. Unwanted interactions are typicallyprevented by providing gaps or trenches that are filled withelectrically insulative material to isolate the elements both physicallyand electrically. As circuit densities increase, however, the widths ofthese gaps decrease, increasing their aspect ratios and making itprogressively more difficult to fill the gaps without leaving voids. Theformation of voids when the gap is not filled completely is undesirablebecause they may adversely affect operation of the completed device,such as by trapping impurities within the insulative material.

Common techniques that are used in such gapfill applications arechemical-vapor deposition (“CVD”) techniques. Conventional thermal CVDprocesses supply reactive gases to the substrate surface whereheat-induced chemical reactions take place to produce a desired film.Plasma-enhanced CVD (“PECVD”) techniques promote excitation and/ordissociation of the reactant gases by the application of radio-frequency(“RF”) energy to a reaction zone near the substrate surface, therebycreating a plasma. The high reactivity of the species in the plasmareduces the energy required for a chemical reaction to take place, andthus lowers the temperature required for such CVD processes whencompared with conventional thermal CVD processes. These advantages maybe further exploited by high-density-plasma (“HDP”) CVD techniques, inwhich a dense plasma is formed at low vacuum pressures so that theplasma species are even more reactive. While each of these techniquesfalls broadly under the umbrella of “CVD techniques,” each of them hascharacteristic properties that make them more or less suitable forcertain specific applications.

HDP-CVD systems form a plasma that is at least approximately two ordersof magnitude greater than the density of a standard, capacitivelycoupled plasma CVD system. Examples of HDP-CVD systems includeinductively coupled plasma systems and electron cyclotron resonance(ECR) plasma systems, among others. HDP-CVD systems generally operate atlower pressure ranges than low-density plasma systems. The low chamberpressure employed in HDP-CVD systems provides active species having along mean-free-path and reduced angular distribution. These factors, incombination with the plasma density, contribute to a significant numberof constituents from the plasma reaching even the deepest portions ofclosely spaced gaps, providing a film with improved gapfill capabilitiescompared with films deposited in a low-density plasma CVD system.

Another factor that allows films deposited by HDP-CVD techniques to haveimproved gapfill characteristics is the promotion of sputtering by thehigh density of the plasma, simultaneous with film deposition. Thesputtering component of HDP deposition processes slows deposition oncertain features, such as the corners of raised surfaces, therebycontributing to the increased gapfill ability of HDP deposited films.Some HDP-CVD systems introduce argon or a similar heavy inert gas tofurther promote the sputtering effect. These HDP-CVD systems typicallyemploy an electrode within the substrate support pedestal that enablesthe creation of an electric field to bias the plasma towards thesubstrate. The electric field can be applied throughout the HDPdeposition process for further promotion of sputtering and to providebetter gapfill characteristics for a given film.

It was initially thought that because of their simultaneousdeposition/sputter nature, HDP-CVD processes could fill the gaps ortrenches that were created in almost any application. Semiconductormanufacturers have discovered, however, that there is a practical limitto the aspect ratio of gaps that HDP-CVD processes are able to fill. Forexample, one HDP-CVD process commonly used to deposit a silicon oxidegapfill film forms a plasma from a process gas that includes silaneSiH₄, molecular oxygen O₂, and argon Ar. It has been reported that whensuch a process is used to fill certain narrow-width high-aspect-ratiogaps, the sputtering caused by argon in the process gas may hamper thegapfill efforts. Specifically, it has been reported that materialsputtered by argon in the process redeposits on the upper portions ofthe sidewalls of the gaps being filled at a rate faster than at thelower portions. This, in turn, may result in the formation of a void inthe gap if the upper areas of regrowth join before the gap is completelyfilled.

FIG. 1 provides schematic cross-sectional views of a silicon oxide filmat different stages of deposition to illustrate the potential gapfilllimitation associated with some CVD processes. The gapfill problem isillustrated in somewhat exaggerated form to illustrate the problembetter. The top portion of FIG. 1 shows the initial structure 104 inwhich a gap 120 is defined by two adjacent features 124 and 128 havinghorizontal surfaces 122, with the horizontal surface at the bottom ofthe gap being denoted 132. As shown in structure 108, i.e. the secondportion of the figure from the top, a conventional HDP-CVD silicon oxidedeposition process results in direct deposition on the horizontalsurface 132 at the bottom of the gap 120 and on the horizontal surfaces122 above the features 124 and 128. It also, however, results inindirect deposition (referred to as “redeposition”) on the sidewalls 140of the gap 120 due to recombination of material sputtered from thesilicon oxide film as it grows. In certain small-width,high-aspect-ratio applications, the continued growth of the siliconoxide film results in formations 136 on the upper section of thesidewall 140 that grow towards each other at a rate of growth exceedingthe rate at which the film grows laterally on the lower portions of thesidewall. This trend is shown in structures 108 and 112, with the finalresult in structure 116 being the formation of a void 144 within thefilm. The probability of forming a void is very directly related to therate and character of the redeposition.

There accordingly remains a general need in the art for improvinggapfill techniques.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention provide methods of depositing a siliconoxide film that improve gapfill capabilities. Some embodiments that areespecially suitable for substrates that have both dense and open areasand fill part of the gaps with an initially higher depositioncontribution from an HDP-CVD process, followed by a lower depositioncontribution to fill a further portion of the gaps. Other embodimentsmake use of an unexpected chemical effect with a hydrogen-based plasmato remove material intermediate between deposition phases to reopen thegap before formation of a void. In some instances, these embodimentsoverlap with certain processes making use of both aspects.

Thus, in a first set of embodiments, a method is provided of depositinga silicon oxide film on a substrate disposed in a substrate processingchamber. The substrate has a gap formed between adjacent raisedsurfaces. A silicon-containing gas, an oxygen-containing gas, and afluent gas are flowed into the substrate processing chamber. The fluentgas has an average molecular weight less than 5 amu. A firsthigh-density plasma is formed from the silicon-containing gas, theoxygen-containing gas, and the fluent gas to deposit a first portion ofthe silicon oxide film over the substrate and within the gap with afirst deposition process that has simultaneous deposition and sputteringcomponents having relative contributions defined by a firstdeposition/sputter ratio. A second high-density plasma is formed fromthe silicon-containing gas, the oxygen-containing gas, and the fluentgas to deposit a second portion of the silicon oxide film over thesubstrate and within the gap with a second deposition process that hassimultaneous deposition and sputtering components having relativecontributions defined by a second deposition/sputter ratio. The seconddeposition/sputter ratio is less than the first deposition/sputterratio. Each of the first and second deposition/sputter ratios is definedas a ratio of a sum of a net deposition rate and a blanket sputteringrate to the blanket sputtering rate.

In some embodiments, the first deposition/sputter ratio is between 20and 100. Also in some embodiments, the second deposition/sputter ratiois less than 10. The second high-density plasma may be formed bychanging process conditions without extinguishing the first high-densityplasma. The fluent gas may comprise molecular hydrogen H₂ and may beflowed into the substrate processing chamber with a flow rate greaterthan 500 sccm. In another embodiment, the fluent gas comprises heliumHe. The silicon-containing gas may comprise monosilane SiH₄ and theoxygen-containing gas may comprise molecular oxygen O₂. In oneembodiment, the first portion of the silicon oxide film reduces a depthof the gap by less than 50%. In some instances, the gap may comprise aplurality of gaps formed between adjacent raised surfaces, with a firstof the gaps having a width at least five times a width of a second ofthe gaps.

In a second set of embodiments, a method is also provided for depositinga silicon oxide film on a substrate disposed in a substrate processingchamber. The substrate has a gap formed between adjacent raisedsurfaces. A flow of a first gaseous mixture is provided to the substrateprocessing chamber. The first gaseous mixture comprises a flow of asilicon-containing gas, a flow of an oxygen-containing gas, and a flowof a fluent gas. A first high-density plasma is formed from the firstgaseous mixture to deposit a first portion of the silicon oxide filmover the substrate and within the gap with a first deposition processthat has simultaneous deposition and sputtering components. The firstportion of the silicon oxide film is exposed to a second high-densityplasma formed with a flow of gases having an average molecular weightless than 5 amu and including a flow of molecular hydrogen H₂.Thereafter, a flow of a second gaseous mixture is provided to thesubstrate processing chamber. The flow of the second gaseous mixturecomprises a flow of a silicon-containing gas, a flow of anoxygen-containing gas, and a flow of a fluent gas. A third high-densityplasma is formed from the second gaseous mixture to deposit a secondportion of the silicon oxide film over the substrate and within the gapwith a second deposition process that has simultaneous deposition andsputtering components.

In some such embodiments, the second high-density plasma is formed witha flow that consists essentially of molecular hydrogen H₂. The firstportion may be exposed to the second high-density plasma by terminatingthe flow of the silicon-containing gas and the flow of theoxygen-containing gas comprised by the flow of the first gaseousmixture. In addition, the flow of the second gaseous mixture may beprovided by reinitiating the terminated flow of the silicon-containinggas and the terminated flow of the oxygen-containing gas. The flow rateof molecular hydrogen H₂ may be provided at a rate greater than 500 sccmin some embodiments, and may be provided at a rate greater than 1000sccm in other embodiments.

The process may be cycled repeatedly. For example, in one embodiment,the second portion of the silicon oxide film is exposed to a fourthhigh-density plasma formed with a flow of gases having an averagemolecular weight less than 5 amu and including a flow of molecularhydrogen. Thereafter, a flow of a third gaseous mixture is provided tothe substrate processing chamber. The flow of the third gaseous mixturecomprises a flow of a silicon-containing gas, a flow of anoxygen-containing gas, and a flow of a fluent gas. A fifth high-densityplasma is formed from the third gaseous mixture to deposit a thirdportion of the silicon oxide film over the substrate and within the gapwith a third deposition process that has simultaneous deposition andsputtering components.

In addition, relative deposition and sputtering contributions may bevaried during different depositions. For example the first depositionprocess may comprise relative deposition and sputtering contributionsdefined by a first deposition/sputter ratio between 20 and 100, and thesecond deposition process may comprise deposition and sputteringcontributions defined by a second deposition/sputter ratio less than 10.In other instance, the first deposition process may comprise a firstpart having relative deposition and sputtering contributions defined bya first deposition/sputter ratio between 20 and 100, followed by asecond part having relative deposition and sputtering contributionsdefined by a second deposition/sputter ratio less than 10. Similarly,the second deposition process may comprise a first part having relativedeposition and sputtering contributions defined by a firstdeposition/sputter ratio between 20 and 100, followed by a second parthaving relative deposition and sputtering contributions defined by asecond deposition/sputter ratio less than 10.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides schematic cross-sectional drawings illustrating theformation of a void during a prior-art gapfill process;

FIG. 2 is a simplified cross-sectional view of a partially completedintegrated circuit that includes a plurality of shallow-trench-isolationstructures;

FIGS. 3A and 3B are schematic diagrams that respectively illustratedgapfill characteristics of densely packed areas and open areas in astructure;

FIG. 4 is a flow diagram illustrating a method for depositing a film inone embodiment of the invention;

FIG. 5 is a flow diagram illustrating a method for depositing a film inanother embodiment of the invention;

FIG. 6 provides schematic diagrams illustrating how material isdeposited in a gap using the method of FIG. 5;

FIGS. 7A-7C are flow diagrams that illustrate alternative methods fordepositing a film in other embodiments of the invention;

FIG. 8A is a simplified diagram of one embodiment of ahigh-density-plasma chemical-vapor-deposition system with which methodsof the invention may be implemented; and

FIG. 8B is a simplified cross section of a gas ring that may be used inconjunction with the exemplary processing system of FIG. 8A.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are directed to methods of depositing asilicon oxide layer to fill a gap in a surface of a substrate using ahigh-density-plasma CVD process. Silicon oxide films deposited accordingto the techniques of the invention have excellent gapfill capabilitiesand are able to fill gaps encountered in, for example,shallow-trench-isolation (“STI”) structures. Films deposited by themethods of the invention are thus suitable for use in the fabrication ofa variety of integrated circuits.

The types of structures that may be filled according to embodiments ofthe invention are illustrated by FIG. 2, which provides a simplifiedcross-sectional view of a partially completed integrated circuit 200.This integrated circuit is formed over a substrate 204 that includes aplurality of STI structures, each of which is typically created byforming a thin pad oxide layer 220 over the surface of the substrate 204and then forming a silicon nitride layer 216 over the pad oxide layer220. The nitride and oxide layers are then patterned using standardphotolithography techniques and trenches 224 are etched through thenitride/oxide stack into the substrate 204. FIG. 2 shows that theintegrated circuit may comprise areas 208 that are relatively denselypacked with transistors or other active devices, and may comprise openareas 212 that are relatively isolated. Active devices in the open areas212 may be separated from each other by more than an order of magnitudethan separations in the densely packed areas 208, but as used herein“open areas” are considered to be areas in which gaps have a width atleast five times a width of a gap in a “dense area.”

Embodiments of the invention provide methods for filling the trenches224 with an electrically insulating material such as silicon dioxideusing a deposition process that has good gapfill properties. Differentembodiments of the invention are more suitable for filling gaps in theopen areas, while other embodiments of the invention are especiallysuitable for filling the very high aspect-ratio gaps in the dense areas.In some instances, the gapfill characteristics provided by the methodsdescribed below have good gapfill capabilities in both the open anddense areas, making such techniques especially valuable for certainapplications. In some instances, prior to the gapfill process, aninitial lining layer is deposited over the substrate as an in situ steamgeneration (“ISSG”) or other thermal oxide layer, or perhaps a siliconnitride layer. One benefit to depositing such a liner prior to fillingthe trenches 224 is to provide appropriate corner rounding, which mayaid in avoiding such effects as early gate breakdown in transistors thatare formed. In addition, such a liner may aid in relieving stress afterthe CVD deposition.

As used herein, a high-density-plasma process is a plasma CVD processthat includes simultaneous deposition and sputtering components and thatemploys a plasma having an ion density on the order of 10¹¹ ions/cm³ orgreater. The relative levels of the combined deposition and sputteringcharacteristics of the high-density plasma may depend on such factors asthe flow rates used to provide the gaseous mixture, the source powerlevels applied to maintain the plasma, the bias power applied to thesubstrate, and the like. The combination of such factors mayconveniently be quantified with a “deposition/sputter ratio,” sometimesdenoted D/S to characterize the process:$\frac{D}{S} \equiv {\frac{( {{net}\quad{deposition}\quad{rate}} ) + ( {{blanket}\quad{sputtering}\quad{rate}} )}{( {{blanket}\quad{sputtering}\quad{rate}} )}.}$The deposition/sputter ratio increases with increased deposition anddecreases with increased sputtering. As used in the definition of D/S,the “net deposition rate” refers to the deposition rate that is measuredwhen deposition and sputtering are occurring simultaneously. The“blanket sputter rate” is the sputter rate measured when the processrecipe is run without deposition gases; the pressure within the processchamber is adjusted to the pressure during deposition and the sputterrate measured on a blanket thermal oxide.

Other equivalent measures may be used to quantify the relativedeposition and sputtering contributions of the HDP process, as is knownto those of skill in the art. A common alternative ratio is the“etching/deposition ratio,”${\frac{E}{D} \equiv \frac{( {{source}\text{-}{only}\quad{deposition}\quad{rate}} ) - ( {{net}\quad{deposition}\quad{rate}} )}{( {{source}\text{-}{deposition}\quad{rate}} )}},$which increases with increased sputtering and decreases with increaseddeposition. As used in the definition of E/D, the “net deposition rate”again refers to the deposition rate measured when deposition andsputtering are occurring simultaneously. The “source-only depositionrate,” however, refers to the deposition rate that is measured when theprocess recipe is run with no sputtering. Embodiments of the inventionare described herein in terms of D/S ratios. While D/S and E/D are notprecise reciprocals, they are inversely related and conversion betweenthem will be understood to those of skill in the art.

The desired D/S ratios for a given step in the HDP-CVD processes aregenerally achieved by including flows of precursor gases and, in someinstances, flows of a fluent gas, which may also act as a sputteringagent. The elements comprised by the precursor gases react to form thefilm with the desired composition. For example, to deposit a siliconoxide film, the precursor gases may include a silicon-containing gas,such as silane SiH₄, and an oxidizing gas reactant such as molecularoxygen O₂. Dopants may be added to the film by including a precursor gaswith the desired dopant, such as by including a flow of SiF₄ tofluorinate the film, including a flow of PH₃ to phosphorate the film,including a flow of B₂H₆ to boronate the film, including a flow of N₂ tonitrogenate the film, and the like. The fluent gas may be provided witha flow of H₂ or with a flow of an inert gas, including a flow of He, oreven a flow a heavier inert gas, such as Ne, Ar, or Xe. The level ofsputtering provided by the different fluent gases is inversely relatedto their atomic mass (or molecular mass in the case of H₂), with H₂producing even less sputtering than He. Embodiments of the inventiongenerally provide fluent-gas flows that have an average molecular massless than 5 amu. This may be achieved by using flows of a singlelow-mass gas, such as with a flow of substantially pure H₂ or with aflow of substantially pure He. Alternatively, flows may sometimes beprovided of multiple gases, such as by providing both a flow of H₂ and aflow of He, which mix in the HDP-CVD process chamber. Alternatively, thegas may sometimes be premixed so that a flow of H₂/He is provided in amixed state to the process chamber. It is also possible to provideseparate flows of higher-mass gases, or to include higher-mass gases inthe premixture, with the relative flow rates and/or concentrations ofthe premixture being selected to maintain an average molecular mass lessthan 5 amu.

In high-aspect-ratio structures, the use of relatively high flow ratesof low-mass fluent gases has been found generally to improve gapfillcapability when compared with the more traditional use of fluent gasessuch as Ar. This is believed to be a consequence of the reduction inredeposition that is achieved by using He or H₂ as a fluent gas so thatclosure of the gap occurs less quickly. The inventors have discovered,however, that the use of such a low-mass fluent gas results in increasedcorner clipping in open regions. This effect may be understood withreference to FIGS. 3A and 3B, which show the effect of the sputteringcomponent of an HDP process respectively for a gap in a densely packedarea and for a gap in an open area.

In particular, the gap 304 in FIG. 3A is a high-aspect-ratio gap, withthe material deposited using an HDP-CVD process forming a characteristiccusp structure 308 over the horizontal surfaces. Redeposition occurs asmaterial 312 is sputtered from the cusp 308 in response to the impact ofplasma ions along path 316. The sputtered material 312 follows a path320 that encounters the sidewall 324 on the opposite side of the gap304. This effect is symmetrical so that as material is sputtered awayfrom the left side of the gap onto the right side, material is alsosputtered away from the right side of the gap onto the left side. Theredeposition of material protects against excess sputtering resulting inclipping of the corners.

This symmetry is not present in the open areas, as illustrated with theopen-area structure 330 shown in FIG. 3B. in this instance, thedeposition causes the formation of a similar cusp 308′, but whenmaterial 312′ is sputtered along path 320′ in response to the impact ofplasma ions along path 316′, the opposite side of the gap is too faraway for the redeposition to be protective. The corner of the structurein FIG. 3B suffers the same ejection of material as does the corner ofthe structure in FIG. 3A, without the compensating effect of receivingmaterial sputtered from the opposite side of the gap. As a consequence,there is an increased risk of clipping the corner and damaging theunderlying structure.

In an embodiment of the invention, such corner clipping is avoided inopen areas by using a process that has an initially high D/S ratio sothat the initial part of the process is dominated by a greaterdeposition component and a reduced sputtering component. Subsequently,after some material has been deposited to protect the underlyingstructure, the D/S ratio is decreased so that the increased sputteringcomponent keeps the gap open as material is deposited to completegapfill. This decrease in D/S ratio during the process is used toaddress a combination of effects resulting from the use of a low-massfluent gas in combination with a gap structure that does not benefit asstrongly from redeposition effects. Such a decrease in D/S ratio isgenerally counter to more traditional gapfill techniques that increasethe D/S ratio to improve gapfill with an initially aggressive gap.

An exemplary process that uses this technique is illustrated with theflow diagram of FIG. 4. The process begins at block 404 by transferringa substrate into a process chamber. The substrate is typically asemiconductor wafer, such as a 200-mm or 300-mm-diameter silicon wafer.Flows of precursor gases are provided to the chamber at block 408,including a flow of a silicon-containing gas, a flow of anoxygen-containing gas, and a flow of a low-mass fluent gas. Table Iprovides exemplary flow rates for deposition of an undoped silicateglass (“USG”) film using flows of monosilane SiH₄, molecular oxygen O₂,and H₂, although it should be understood that other precursor gases,including dopant sources, and other fluent gases that provide an averagemolecular mass less than 5 amu may be used as discussed above. TABLE IExemplary Flow Rates for USG Deposition Flow Rates for 200-mm Flow Ratesfor 300-mm Wafer Process Wafer Process F(SiH₄) 10-60 sccm F(SiH₄) 10-60sccm F(O₂) 20-120 sccm F(O₂) 20-120 sccm F(H₂) 400-1000 sccm F(H₂)750-1600 sccmAs the table indicates, the flow rates of the precursor gases may besimilar for 200-mm and 300-mm-diameter wafers, but the flow rate of thefluent gas is generally higher.

A high-density plasma is formed from the gaseous flows at block 412 bycoupling energy into the chamber. A common technique for generating ahigh-density plasma is to couple rf energy inductively. The D/S ratio isdetermined not only by the flow rates for the gases, but also by thepower density of energy coupled into the chamber, by the strength of abias that may be applied to the substrate, by the temperature within thechamber, by the pressure within the chamber, and other such factors. Fordeposition of an initial portion of the film, such processing parametersare selected to provide a D/S ratio within the range of 20-100, asindicated at block 416. Deposition is permitted to proceed with such aD/S ratio to fill the gap partially, as indicated at block 420, with theprocess conditions being changed to provide a lower D/S ratio at block424. In some embodiments, the gap is filled at block 420 so that itsdepth is reduced by less than 50% from its initial depth. For instance,if the gap had an initial depth of 5.4 μm, as might occur for a gaphaving an aspect ratio of 6:1 and a width of about 0.90 μm, the fillingat block 420 might reduce the depth of the gap to about 3.3 μm, areduction in the height of about 40%.

Suitable values for the D/S ratio to fill the remainder of the gap atblock 428 are values less than 10, as indicated at block 424. Thesevalues are again determined by the processing parameters and provide anincreased sputtering component to keep the gap open during deposition ofthe remainder of the film. After the gap has been filled, the plasma isextinguished at block 432 and the substrate is transferred out of theprocess chamber at block 436.

The process has thus been described as an in situ process taking placein a single chamber with a continuous plasma, but these are notrequirements of the invention. In alternative embodiments, the plasmamay be extinguished and reinitiated for different parts of the processand the different parts of the process may be performed in differentchambers.

Another embodiment of the invention is illustrated with the flow diagramof FIG. 5 and makes use of an unexpected discovery by the inventors thata hydrogen plasma may be used to remove deposited silicon oxide. Theremoval proceeds chemically according to the reaction SiO₂+2H₂→SiH₄+O₂and provides a relatively slow removal rate of about 50-100 Å/min, evenwith a H₂ flow rate to the chamber on the order of 1000 sccm. This slowremoval rate provides an improved degree of precision over the removalprocess that is not available with alternative removal processes, suchas chemical etching processes based on halogen chemistry or mechanicalprocesses that provide processing conditions with a low D/S ratio tosputter material aggressively. The use of halogen-based etchchemistries, such as result from plasmas formed from flows of NF₃, maycause undesirable stress on the chamber ceramics because of theformation of aluminum halogen byproducts such as AlF₃.

In describing these embodiments, reference is made simultaneously to theflow diagram of FIG. 5 and to FIG. 6, which provides simplifiedcross-sectional views of a structure at different points during theprocess described in connection with FIG. 5. The structure is shown as asubstrate having trenches etched therein as part of an STI structure,but the principles described herein may be applied more generally to anystructure that defines gaps to be filled, including IMD and PMDapplications, among others. As shown in FIG. 5, the process starts bypositioning a substrate in a process chamber at block 504. The substratehas an initial structure 604 shown schematically in FIG. 6 with features620 that form one or more gaps to be filled. The features 620 may be,for example, areas of a substrate between etched trenches, adjacentmetal lines, transistor gates, or other features. In some instances, thestructure 604 may additionally include silicon nitride portions abovethe raised features and/or a silicon nitride liner along the interior ofthe gaps. The presence of such a line may increase the aspect ratio ofthe gap even further.

Once the substrate is properly positioned, flows of a silicon-containinggas like SiH₄, an oxygen-containing gas like O₂, and molecular hydrogenH₂ are provided to the chamber at block 508. A high-density plasma isformed from the gas flows by inductively coupling rf energy into thechamber at block 512, permitting the gap to be partially filled at block516. As explained above, the deposition at block 516 results in theformation of a cusp 636, as shown for intermediate structure 608, withredeposition causing silicate glass to be deposited more thickly nearthe corners of the underlying structures than on the sidewalls.

To remove some of the deposited silicate glass and reshape the gap forfurther deposition, the flows of the precursor silicon-containing andoxygen-containing gases, as well as flows of any dopant gases that mayhave been supplied, are terminated at block 520. The removal of materialresults from the chemical interaction of the remaining hydrogen plasmato produce a further intermediate structure 612 that has a reduced cuspheight 640 and a reshaped profile. While the principal removal mechanismresults from the chemical interaction described above, it may beenhanced in certain embodiments. For instance, a bias may be applied tothe substrate to attract the plasma ions and thereby introduce ananisotropy in the removal. Other anisotropies may be introduced by usingdifferent flows of the H₂ gas into the chamber to provide different flowcharacteristics throughout the chamber, allowing the removal to beperformed selectively across the substrate as a whole. In addition, theplasma may comprise species other than hydrogen to increase themechanical sputtering effect, although some embodiments of the inventiongenerally remain limited to instances in which the average molecularweight of the sources is less than 5 amu.

Removal of material results in structure 612 by shaping the depositedfilm 640 so that the basic shape of the original features is retained,but with a less severe aspect ratio. After material has been removed toreopen the gap, flows of the precursor gases are reinitiated at block528 so that the remainder of the gap may be filled at block 532 toproduce structure 616 with film 644 providing substantially void-freegapfill. In many instances, the gap may be filled with two suchdeposition stages and a single intermediate removal stage, although moreaggressive gaps may be filled with a greater number of interleaveddeposition and removal stages. After the gap has been filled, thesubstrate is transferred out of the chamber at block 536.

Again, the process has been described as an in situ process in which thedeposition and removal stages are performed in a single chamber with acontinuous plasma. In other embodiments, the plasma may be extinguishedbetween stages, with gas flows and other parameters being adjusted inpreparation for the next phase, and a plasma being reformed. Suchembodiments may also be performed as in situ processes in a singlechamber (or in different chambers of a multichamber system), or may beperformed as ex situ processes in different chambers. In some instances,in situ processes are preferred for throughput and performance reasons.

In other embodiments, the processes described in connection with FIG. 4regarding the use of a decreasing D/S ratio and the processes describedin connection with FIG. 5 regarding the chemical removal ofsilicate-glass material with a hydrogen-based plasma may be combined.FIGS. 7A-7C each provide flow diagrams that illustrate how the processesmay be combined in different ways.

First, the change in D/S ratio used in FIG. 4 may be integrated with theprocess of FIG. 5 by having either or both of the depositions 516 and/or532 use change in D/S ratio. Thus, FIG. 7A illustrates explicitly thatblock 516 of FIG. 5 may comprise a first block 762 at which a firstportion of the gap is filled with process conditions that provide a D/Sratio between 20 and 100 and a second block 764 at which a secondportion of the gap is thereafter filled with process conditions thatprovide a D/S ratio less than 10. The inclusion of such an initiallyhigh D/S ratio is useful in avoiding corner clipping in open areas forthe same reasons that were described above.

FIG. 7B similarly illustrates explicitly that block 532 of FIG. 5 maycomprise a first block 766 at which a first portion of the gap is filledwith process conditions that provide a D/S ratio between 20 and 100 anda second block 768 at which a second portion of the gap is thereafterfilled with process conditions that provide a D/S ratio less than 10.The inclusion of such a high D/S ratio after the removal of material atblock 524 of FIG. 5 may be useful under circumstances where the amountof material removed poses a risk of corner clipping in open areasbecause of the presence of insufficient material to protect the corners.

FIG. 7C illustrates a process in which the high D/S ratio is usedinitially, thereby providing protection against corner clipping in openareas, but uses the lower D/S ratio after the removal of material byexposure to a hydrogen plasma. Such an embodiment is suitable inapplications where the removal of material is not so aggressive as topresent a risk of corner clipping, even in open areas, there beingsufficient silicate glass material remaining even after the removal toprotect the corners. To perform such a process as an in situ processwith a continuous plasma, the substrate is transferred into the chamberat block 704 and flows of a silicon-containing gas, an oxygen-containinggas, and H₂ are provided at block 708 so that a high-density plasma maybe formed in the chamber at block 712. The gap is partially filled atblock 716 using process parameters that provide a D/S ratio between 20and 100. Flows of the precursor silicon-containing and oxygen-containinggases are terminated at block 720 so that part of the deposited film maybe removed with a hydrogen plasma at block 724. The flows of theprecursor silicon-containing and oxygen-containing gases are reinitiatedat block 728, and the process parameters are established so that theremainder of the gap is filled at block 732 with a D/S ratio less than10. After completing the gap fill process, the substrate is transferredout of the chamber at block 736.

Exemplary Substrate Processing System

The inventors have implemented embodiments of the invention with theULTIMA™ system manufactured by APPLIED MATERIALS, INC., of Santa Clara,Calif., a general description of which is provided in commonly assignedU.S. Pat. No. 6,170,428, “SYMMETRIC TUNABLE INDUCTIVELY COUPLED HDP-CVDREACTOR,” filed Jul. 15, 1996 by Fred C. Redeker, Farhad Moghadam,Hirogi Hanawa, Tetsuya Ishikawa, Dan Maydan, Shijian Li, Brian Lue,Robert Steger, Yaxin Wang, Manus Wong and Ashok Sinha, the entiredisclosure of which is incorporated herein by reference. An overview ofthe system is provided in connection with FIGS. 8A and 8B below. FIG. 8Aschematically illustrates the structure of such an HDP-CVD system 810 inone embodiment. The system 810 includes a chamber 813, a vacuum system870, a source plasma system 880A, a bias plasma system 880B, a gasdelivery system 833, and a remote plasma cleaning system 850.

The upper portion of chamber 813 includes a dome 814, which is made of aceramic dielectric material, such as aluminum oxide or aluminum nitride.Dome 814 defines an upper boundary of a plasma processing region 816.Plasma processing region 816 is bounded on the bottom by the uppersurface of a substrate 817 and a substrate support member 818.

A heater plate 823 and a cold plate 824 surmount, and are thermallycoupled to, dome 814. Heater plate 823 and cold plate 824 allow controlof the dome temperature to within about ±10° C. over a range of about100° C. to 200° C. This allows optimizing the dome temperature for thevarious processes. For example, it may be desirable to maintain the domeat a higher temperature for cleaning or etching processes than fordeposition processes. Accurate control of the dome temperature alsoreduces the flake or particle counts in the chamber and improvesadhesion between the deposited layer and the substrate.

The lower portion of chamber 813 includes a body member 822, which joinsthe chamber to the vacuum system. A base portion 821 of substratesupport member 818 is mounted on, and forms a continuous inner surfacewith, body member 822. Substrates are transferred into and out ofchamber 813 by a robot blade (not shown) through an insertion/removalopening (not shown) in the side of chamber 813. Lift pins (not shown)are raised and then lowered under the control of a motor (also notshown) to move the substrate from the robot blade at an upper loadingposition 857 to a lower processing position 856 in which the substrateis placed on a substrate receiving portion 819 of substrate supportmember 818. Substrate receiving portion 819 includes an electrostaticchuck 820 that secures the substrate to substrate support member 818during substrate processing. In a preferred embodiment, substratesupport member 818 is made from an aluminum oxide or aluminum ceramicmaterial.

Vacuum system 870 includes throttle body 825, which houses twin-bladethrottle valve 826 and is attached to gate valve 827 and turbo-molecularpump 828. It should be noted that throttle body 825 offers minimumobstruction to gas flow, and allows symmetric pumping. Gate valve 827can isolate pump 828 from throttle body 825, and can also controlchamber pressure by restricting the exhaust flow capacity when throttlevalve 826 is fully open. The arrangement of the throttle valve, gatevalve, and turbo-molecular pump allow accurate and stable control ofchamber pressures up to about 1 millitorr to about 2 torr.

The source plasma system 880A includes a top coil 829 and side coil 830,mounted on dome 814. A symmetrical ground shield (not shown) reduceselectrical coupling between the coils. Top coil 829 is powered by topsource RF (SRF) generator 831A, whereas side coil 830 is powered by sideSRF generator 831B, allowing independent power levels and frequencies ofoperation for each coil. This dual coil system allows control of theradial ion density in chamber 813, thereby improving plasma uniformity.Side coil 830 and top coil 829 are typically inductively driven, whichdoes not require a complimentary electrode. In a specific embodiment,the top source RF generator 831A provides up to 2,500 watts of RF powerat nominally 2 MHz and the side source RF generator 831B provides up to5,000 watts of RF power at nominally 2 MHz. The operating frequencies ofthe top and side RF generators may be offset from the nominal operatingfrequency (e.g. to 1.7-1.9 MHz and 1.9-2.1 MHz, respectively) to improveplasma-generation efficiency.

A bias plasma system 880B includes a bias RF (“BRF”) generator 831C anda bias matching network 832C. The bias plasma system 880B capacitivelycouples substrate portion 817 to body member 822, which act ascomplimentary electrodes. The bias plasma system 880B serves to enhancethe transport of plasma species (e.g., ions) created by the sourceplasma system 880A to the surface of the substrate. In a specificembodiment, bias RF generator provides up to 10,000 watts of RF power ata frequency less than 5 MHz, as discussed further below.

RF generators 831A and 831B include digitally controlled synthesizersand operate over a frequency range between about 1.8 to about 2.1 MHz.Each generator includes an RF control circuit (not shown) that measuresreflected power from the chamber and coil back to the generator andadjusts the frequency of operation to obtain the lowest reflected power,as understood by a person of ordinary skill in the art. RF generatorsare typically designed to operate into a load with a characteristicimpedance of 50 ohms. RF power may be reflected from loads that have adifferent characteristic impedance than the generator. This can reducepower transferred to the load. Additionally, power reflected from theload back to the generator may overload and damage the generator.Because the impedance of a plasma may range from less than 5 ohms toover 900 ohms, depending on the plasma ion density, among other factors,and because reflected power may be a function of frequency, adjustingthe generator frequency according to the reflected power increases thepower transferred from the RF generator to the plasma and protects thegenerator. Another way to reduce reflected power and improve efficiencyis with a matching network.

Matching networks 832A and 832B match the output impedance of generators831A and 831B with their respective coils 829 and 830. The RF controlcircuit may tune both matching networks by changing the value ofcapacitors within the matching networks to match the generator to theload as the load changes. The RF control circuit may tune a matchingnetwork when the power reflected from the load back to the generatorexceeds a certain limit. One way to provide a constant match, andeffectively disable the RF control circuit from tuning the matchingnetwork, is to set the reflected power limit above any expected value ofreflected power. This may help stabilize a plasma under some conditionsby holding the matching network constant at its most recent condition.

Other measures may also help stabilize a plasma. For example, the RFcontrol circuit can be used to determine the power delivered to the load(plasma) and may increase or decrease the generator output power to keepthe delivered power substantially constant during deposition of a layer.

A gas delivery system 833 provides gases from several sources, 834A-834Echamber for processing the substrate via gas delivery lines 838 (onlysome of which are shown). As would be understood by a person of skill inthe art, the actual sources used for sources 834A-834E and the actualconnection of delivery lines 838 to chamber 813 varies depending on thedeposition and cleaning processes executed within chamber 813. Gases areintroduced into chamber 813 through a gas ring 837 and/or a top nozzle845. FIG. 8B is a simplified, partial cross-sectional view of chamber813 showing additional details of gas ring 837.

In one embodiment, first and second gas sources, 834A and 834B, andfirst and second gas flow controllers, 835A′ and 835B′, provide gas toring plenum 836 in gas ring 837 via gas delivery lines 838 (only some ofwhich are shown). Gas ring 837 has a plurality of source gas nozzles 839(only one of which is shown for purposes of illustration) that provide auniform flow of gas over the substrate. Nozzle length and nozzle anglemay be changed to allow tailoring of the uniformity profile and gasutilization efficiency for a particular process within an individualchamber. In a preferred embodiment, gas ring 837 has 12 source gasnozzles made from an aluminum oxide ceramic.

Gas ring 837 also has a plurality of oxidizer gas nozzles 840 (only oneof which is shown), which in a preferred embodiment are co-planar withand shorter than source gas nozzles 839, and in one embodiment receivegas from body plenum 841. In some embodiments it is desirable not to mixsource gases and oxidizer gases before injecting the gases into chamber813. In other embodiments, oxidizer gas and source gas may be mixedprior to injecting the gases into chamber 813 by providing apertures(not shown) between body plenum 841 and gas ring plenum 836. In oneembodiment, third, fourth, and fifth gas sources, 834C, 834D, and 834D′,and third and fourth gas flow controllers, 835C and 835D′, provide gasto body plenum via gas delivery lines 838. Additional valves, such as843B (other valves not shown), may shut off gas from the flowcontrollers to the chamber. In implementing certain embodiments of theinvention, source 834A comprises a silane SiH₄ source, source 834Bcomprises a molecular oxygen O₂ source, source 834C comprises a silaneSiH₄ source, source 834D comprises a helium He source, and source 834D′comprises a molecular hydrogen H₂ source.

In embodiments where flammable, toxic, or corrosive gases are used, itmay be desirable to eliminate gas remaining in the gas delivery linesafter a deposition. This may be accomplished using a 3-way valve, suchas valve 843B, to isolate chamber 813 from delivery line 838A and tovent delivery line 838A to vacuum foreline 844, for example. As shown inFIG. 8A, other similar valves, such as 843A and 843C, may beincorporated on other gas delivery lines. Such three-way valves may beplaced as close to chamber 813 as practical, to minimize the volume ofthe unvented gas delivery line (between the three-way valve and thechamber). Additionally, two-way (on-off) valves (not shown) may beplaced between a mass flow controller (“MFC”) and the chamber or betweena gas source and an MFC.

Referring again to FIG. 8A, chamber 813 also has top nozzle 845 and topvent 846. Top nozzle 845 and top vent 846 allow independent control oftop and side flows of the gases, which improves film uniformity andallows fine adjustment of the film's deposition and doping parameters.Top vent 846 is an annular opening around top nozzle 845. In oneembodiment, first gas source 834A supplies source gas nozzles 839 andtop nozzle 845. Source nozzle MFC 835A′ controls the amount of gasdelivered to source gas nozzles 839 and top nozzle MFC 835A controls theamount of gas delivered to top gas nozzle 845. Similarly, two MFCs 835Band 835B′ may be used to control the flow of oxygen to both top vent 846and oxidizer gas nozzles 840 from a single source of oxygen, such assource 834B. In some embodiments, oxygen is not supplied to the chamberfrom any side nozzles. The gases supplied to top nozzle 845 and top vent846 may be kept separate prior to flowing the gases into chamber 813, orthe gases may be mixed in top plenum 848 before they flow into chamber813. Separate sources of the same gas may be used to supply variousportions of the chamber.

A remote microwave-generated plasma cleaning system 850 is provided toperiodically clean deposition residues from chamber components. Thecleaning system includes a remote microwave generator 851 that creates aplasma from a cleaning gas source 834E (e.g., molecular fluorine,nitrogen trifluoride, other fluorocarbons or equivalents) in reactorcavity 853. The reactive species resulting from this plasma are conveyedto chamber 813 through cleaning gas feed port 854 via applicator tube855. The materials used to contain the cleaning plasma (e.g., cavity 853and applicator tube 855) must be resistant to attack by the plasma. Thedistance between reactor cavity 853 and feed port 854 should be kept asshort as practical, since the concentration of desirable plasma speciesmay decline with distance from reactor cavity 853. Generating thecleaning plasma in a remote cavity allows the use of an efficientmicrowave generator and does not subject chamber components to thetemperature, radiation, or bombardment of the glow discharge that may bepresent in a plasma formed in situ. Consequently, relatively sensitivecomponents, such as electrostatic chuck 820, do not need to be coveredwith a dummy wafer or otherwise protected, as may be required with an insitu plasma cleaning process. In FIG. 8A, the plasma-cleaning system 850is shown disposed above the chamber 813, although other positions mayalternatively be used.

A baffle 861 may be provided proximate the top nozzle to direct flows ofsource gases supplied through the top nozzle into the chamber and todirect flows of remotely generated plasma. Source gases provided throughtop nozzle 845 are directed through a central passage 862 into thechamber, while remotely generated plasma species provided through thecleaning gas feed port 854 are directed to the sides of the chamber 813by the baffle 861.

Those of ordinary skill in the art will realize that specific parameterscan vary for different processing chambers and different processingconditions, without departing from the spirit of the invention. Othervariations will also be apparent to persons of skill in the art. Theseequivalents and alternatives are intended to be included within thescope of the present invention. Therefore, the scope of this inventionshould not be limited to the embodiments described, but should insteadbe defined by the following claims.

1. A method of depositing a silicon oxide film on a substrate disposedin a substrate processing chamber, the substrate having a gap formedbetween adjacent raised surfaces, the method comprising: flowing asilicon-containing gas into the substrate processing chamber; flowing anoxygen-containing gas into the substrate processing chamber; flowing afluent gas having an average molecular weight less than 5 amu into thesubstrate processing chamber; forming a first high-density plasma fromthe silicon-containing gas, the oxygen-containing gas, and the fluentgas to deposit a first portion of the silicon oxide film over thesubstrate and within the gap with a first deposition process that hassimultaneous deposition and sputtering components having relativecontributions defined by a first deposition/sputter ratio; and forming asecond high-density plasma from the silicon-containing gas, theoxygen-containing gas, and the fluent gas to deposit a second portion ofthe silicon oxide film over the substrate and within the gap with asecond deposition process that has simultaneous deposition andsputtering components having relative contributions defined by a seconddeposition/sputter ratio, wherein the second deposition/sputter ratio isless than the first deposition/sputter ratio, wherein each of the firstand second deposition/sputter ratios is defined as a ratio of a sum of anet deposition rate and a blanket sputtering rate to the blanketsputtering rate.
 2. The method recited in claim 1 wherein the firstdeposition/sputter ratio is between 20 and
 100. 3. The method recited inclaim 2 wherein the second deposition/sputter ratio is less than
 10. 4.The method recited in claim 1 wherein forming the second high-densityplasma comprising changing process conditions without extinguishing thefirst high-density plasma.
 5. The method recited in claim 1 wherein thefluent gas comprises molecular hydrogen H₂.
 6. The method recited inclaim 5 wherein the molecular hydrogen H₂ is flowed into the substrateprocessing chamber with a flow rate greater than 500 sccm.
 7. The methodrecited in claim 1 wherein the fluent gas comprises helium He.
 8. Themethod recited in claim 1 wherein the silicon-containing gas comprisesmonosilane SiH₄ and the oxygen-containing gas comprises molecular oxygenO₂.
 9. The method recited in claim 1 wherein the first portion of thesilicon oxide film reduces a depth of the gap by less than 50%.
 10. Themethod recited in claim 1 wherein the gap comprises a plurality of gapsformed between adjacent raised surfaces, a first of the gaps having awidth at least five times a width of a second of the gaps.
 11. A methodof depositing a silicon oxide film on a substrate disposed in asubstrate processing chamber, the substrate having a plurality of gapsformed between adjacent raised surfaces, a first of the gaps having awidth at least five times a width of a second of the gaps, the methodcomprising: flowing monosilane SiH₄ into the substrate processingchamber; flowing molecular oxygen O₂ into the substrate processingchamber; flowing molecular hydrogen H₂ into the substrate processingchamber at a flow rate greater than 500 sccm; forming a firsthigh-density plasma from the monosilane SiH₄, the molecular oxygen O₂,and the molecular hydrogen H₂ to deposit a first portion of the siliconoxide film over the substrate and within each of the first and secondgaps with a first deposition process that has simultaneous depositionand sputtering components having relative contributions defined by afirst deposition/sputter ratio between 20 and 100; and forming a secondhigh-density plasma from the monosilane SiH₄, the molecular oxygen O₂,and the molecular hydrogen H₂ to deposit a second portion of the siliconoxide film over the substrate and within each of the first and secondgaps with a second deposition process that has simultaneous depositionand sputtering having relative contributions defined by a seconddeposition/sputter ratio less than 10, wherein each of the first andsecond deposition/sputter ratios is defined as a ratio of a sum of a netdeposition rate and a blanket sputtering rate to the blanket sputteringrate.
 12. A method of depositing a silicon oxide film on a substratedisposed in a substrate processing chamber, the substrate having a gapformed between adjacent raised surfaces, the method comprising:providing a flow of a first gaseous mixture to the substrate processingchamber, the flow of the first gaseous mixture comprising a flow of asilicon-containing gas, a flow of an oxygen-containing gas, and a flowof a fluent gas; forming a first high-density plasma from the firstgaseous mixture to deposit a first portion of the silicon oxide filmover the substrate and within the gap with a first deposition processthat has simultaneous deposition and sputtering components; exposing thefirst portion of the silicon oxide film to a second high-density plasmaformed with a flow of gases having an average molecular weight less than5 amu and including a flow of molecular hydrogen H₂; thereafter,providing a flow of a second gaseous mixture to the substrate processingchamber, the flow of the second gaseous mixture comprising a flow of asilicon-containing gas, a flow of an oxygen-containing gas, and a flowof a fluent gas; and forming a third high-density plasma from the secondgaseous mixture to deposit a second portion of the silicon oxide filmover the substrate and within the gap with a second deposition processthat has simultaneous deposition and sputtering components.
 13. Themethod recited in claim 12 wherein the second high-density plasma isformed with a flow that consists essentially of molecular hydrogen H₂.14. The method recited in claim 12 wherein exposing the first portion tothe second high-density plasma comprises terminating the flow of thesilicon-containing gas and the flow of the oxygen-containing gascomprised by the flow of the first gaseous mixture.
 15. The methodrecited in claim 14 wherein providing the flow of the second gaseousmixture comprises reinitiating the terminated flow of thesilicon-containing gas and the terminated flow of the oxygen-containinggas.
 16. The method recited in claim 12 wherein the flow of molecularhydrogen H₂ is provided at a rate greater than 500 sccm.
 17. The methodrecited in claim 12 wherein the flow of molecular hydrogen H₂ isprovided at a rate greater than 1000 sccm.
 18. The method recited inclaim 12 further comprising: exposing the second portion of the siliconoxide film to a fourth high-density plasma formed with a flow of gaseshaving an average molecular weight less than 5 amu and including a flowof molecular hydrogen H₂; thereafter, providing a flow of a thirdgaseous mixture to the substrate processing chamber, the flow of thethird gaseous mixture comprising a flow of a silicon-containing gas, aflow of an oxygen-containing gas, and a flow of a fluent gas; andforming a fifth high-density plasma from the third gaseous mixture todeposit a third portion of the silicon oxide film over the substrate andwithin the gap with a third deposition process that has simultaneousdeposition and sputtering components.
 19. The method recited in claim 12wherein: the first deposition process comprises relative deposition andsputtering contributions defined by a first deposition/sputter ratiobetween 20 and 100; the second deposition process comprises relativedeposition and sputtering contributions defined by a seconddeposition/sputter ratio less than 10; and each of the first and seconddeposition/sputter ratios is defined as a ratio of a sum of a netdeposition rate and a blanket sputtering rate to the blanket sputteringrate.
 20. The method recited in claim 12 wherein the first depositionprocess comprises: a first part having relative deposition andsputtering contributions defined by a first deposition/sputter ratiobetween 20 and 100; and a second part having relative deposition andsputtering contributions defined by a second deposition/sputter ratioless than 10, wherein the second part temporally follows the first partand each of the first and second deposition/sputter ratios is defined asa ratio of a sum of a net deposition rate and a blanket sputtering rateto the blanket sputtering rate.
 21. The method recited in claim 12wherein the second deposition process comprises: a first part havingrelative deposition and sputtering contributions defined by a firstdeposition/sputter ratio between 20 and 100; and a second part havingrelative deposition and sputtering contributions defined by a seconddeposition/sputter ratio less than 10, wherein the second parttemporally follows the first part and each of the first and seconddeposition/sputter ratios is defined as a ratio of a sum of a netdeposition rate and a blanket sputtering rate to the blanket sputteringrate.
 22. A method of depositing a silicon oxide film on a substratedisposed in a substrate processing chamber, the substrate having a gapformed between adjacent raised surfaces, the method comprising:providing a flow of a first gaseous mixture to the substrate processingchamber, the flow of the first gaseous mixture comprising a flow ofmonosilane SiH₄, a flow of molecular oxygen O₂, and a flow of molecularhydrogen H₂ at a flow rate greater than 500 sccm; forming a firsthigh-density plasma from the first gaseous mixture to deposit a firstportion of the silicon oxide film over the substrate and within the gapwith a first deposition process that has simultaneous deposition andsputtering components; terminating the flow of the monosilane SiH₄ andthe flow of the molecular oxygen O₂ to expose the first portion of thesilicon oxide film to a second high-density plasma formed from the flowof the molecular hydrogen H₂, wherein the flow rate of the molecularhydrogen H₂ is maintained greater than 500 sccm; reinitiating theterminated flow of the monosilane SiH₄ and the terminated flow of themolecular oxygen O₂ to form a third high-density plasma to deposit asecond portion of the silicon oxide film over the substrate and withinthe gap with a second deposition process that has simultaneousdeposition and sputtering components.
 23. The method recited in claim 22wherein: the gap comprises a plurality of gaps formed between adjacentraised surfaces, a first of the gaps having a width at least five timesa width of a second of the gaps; the first deposition process comprisesrelative deposition and sputtering contributions defined by a firstdeposition/sputter ratio between 20 and 100; and the second depositionprocess comprises relative deposition and sputtering contributionsdefined by a second deposition/sputter ratio less than 10, each of thefirst and second deposition/sputter ratios being defined as a ratio of asum of a net deposition rate and a blanket sputtering rate to theblanket sputtering rate.
 24. A method of depositing a silicon oxide filmon a substrate disposed in a substrate processing chamber, the substratehaving a gap formed between adjacent raised surfaces, the methodcomprising: providing a flow of a first gaseous mixture to the substrateprocessing chamber, the flow of the first gaseous mixture comprising aflow of a silicon-containing gas, a flow of an oxygen-containing gas,and a flow of a fluent gas; forming a first high-density plasma from thefirst gaseous mixture to deposit a first portion of the silicon oxidefilm over the substrate and within the gap with a first depositionprocess that has simultaneous deposition and sputtering components;exposing the first portion of the silicon oxide film to a secondhigh-density plasma formed with a flow of gases that includes a flow ofmolecular hydrogen H₂ and does not include a halogen; thereafter,providing a flow of a second gaseous mixture to the substrate processingchamber, the flow of the second gaseous mixture comprising a flow of asilicon-containing gas, a flow of an oxygen-containing gas, and a flowof a fluent gas; and forming a third high-density plasma from the secondgaseous mixture to deposit a second portion of the silicon oxide filmover the substrate and within the gap with a second deposition processthat has simultaneous deposition and sputtering components.